Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface in accordance with the present design.

The broken line perimeter in the FIGURE represents both the boundariesof the display screen and the graphical user interface. In the FIGURE,this outer edge of the portion of the display screen is understood to becongruent with the outer edge of the graphical user interface.

The text in dotted lines and the broken lines shown in the drawingsillustrate portions of the display screen or portion thereof with agraphical user interface that forms no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.